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The increasing global market size of high-energy storage devices due to the boom in electric vehicles and portable electronics has caused the battery industry to produce a lot of waste lithium-ion batteries. The liberation and de-agglomeration of cathode material are the necessary procedures to improve the recycling derived from spent lithium-ion batteries, as well as enabling the direct recycling pathway. In this study, the supercritical (SC) CO2 was innovatively adapted to enable the recycling of spent lithium-ion batteries (LIBs) based on facilitating the interaction with a binder and dimethyl sulfoxide (DMSO) co-solvent. The results show that the optimum experimental conditions to liberate the cathode particles are processing at a temperature of 70 °C and 80 bar pressure for a duration of 20 min. During the treatment, polyvinylidene fluoride (PVDF) was dissolved in the SC fluid system and collected in the dimethyl sulfoxide (DMSO), as detected by the Fourier Transform Infrared Spectrometer (FTIR). The liberation yield of the cathode from the current collector reaches 96.7% under optimal conditions and thus, the cathode particles are dispersed into smaller fragments. Afterwards, PVDF can be precipitated and reused. In addition, there is no hydrogen fluoride (HF) gas emission due to binder decomposition in the suggested process. The proposed SC-CO2 and co-solvent system effectively separate the PVDF from Li-ion battery electrodes. Thus, this approach is promising as an alternative pre-treatment method due to its efficiency, relatively low energy consumption, and environmental benign features. [ABSTRACT FROM AUTHOR]

In this work, the assembly behavior and structure of a compound collector with different carboxyl group positions at the low-rank coal (LRC)–water interface were investigated through coarse-grained molecular dynamics simulation (CGMD) combined with sum-frequency vibration spectroscopy (SFG). The choice of compound collector was dodecane +decanoic acid (D-DA) and dodecane +2-butyl octanoic acid (D-BA). CGMD results showed that the carboxyl group at the carbon chain's middle can better control the assembly process between carboxylic acid and D molecules. SFG research found that the carboxyl group at the carbon chain's termination had a greater impact on the displacement of the methyl/methylene symmetric stretching vibration peak, while the carboxyl group at the carbon chain's middle had a greater impact on the displacement of the methyl/methylene asymmetric stretching vibration peak. The spatial angle calculation results revealed that the methyl group's orientation angle in the D-BA molecule was smaller and the carboxyl group's orientation angle in the BA molecule was bigger, indicating that D-BA spread more flatly on the LRC surface than D-DA. This meant that the assembled structure had a larger effective adsorption area on the LRC surface. The flotation studies also verified that the assembly behavior and structure of D-BA with the carboxyl group at the carbon chain's middle at the LRC–water interface were more conducive to the improvement of flotation efficiency. The study of interface assembly behavior and structure by CGMD combined with SFG is crucial for the creation of effective compound collectors. [ABSTRACT FROM AUTHOR]

High-ash coal, also known as low-grade coal, has becomes a viable alternative in recent years to high-quality coal because available resources have become increasingly scarce due to extensive mining activity. This work aims to provide a comprehensive understanding of the structural characteristics of high-ash coal and construct a plausible molecular structure to elucidate its chemical reactivity in future applications. Its properties were investigated using Solid-state 13C nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy analysis (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The molecular structure was constructed and validated using Material Studio, LAMMPS Software Package, and MATLAB program. The characterization results revealed that high-ash coal contains 72.15% aromatic carbon, significantly surpassing the percentage of aliphatic carbon (27.85%). The ratio of bridgehead carbon to peripheral aromatic carbon was calculated as 0.67, indicating that the pentacene is the main carbon skeleton form in the high-ash coal structure. Furthermore, oxygen-containing functional groups presented as C=O/O–C–O, C–O, and COO– within the structure along with pyridine and pyrrolic structures. Consequently, the molecular structure comprises pentacene with aliphatic carbon chains, such as methylene, that connect the benzene rings and form a three-dimensional network. The results of a simulated IR spectrum and contact angle simulation aligned with the experimental results, validating the molecular structure of high-ash coal. The chemical formula for the high-ash coal model was determined as C203H189N7O61S with a molecular weight of 3734.79. [ABSTRACT FROM AUTHOR]

The transformation of kaolinite into metakaolinite by thermal activation to obtain highly active aluminosilicate is commonly known. In addition to kaolin, the high content of kaolinite in coal mining waste is another potential source for obtaining an aluminosilicate precursor, thereby protecting the environment and adding value to industrial wastes. In this paper, the kaolinite-based high ash slime (KAS) was calcined at temperatures ranging from 400 °C to 1000 °C under air, N2, and CO2 atmospheres, respectively. The thermal behaviors and structural evolution of each component in KAS were analyzed by thermal analysis (TG-DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Moreover, the chemical reactivity of Al2O3 and SiO2 in calcined KAS was evaluated by HCl and NaOH leaching methods. The results show that the applied KAS in this study primarily consisted of kaolinite and carbon, while the minor mineral phases included quartz, calcite, and pyrite. Additionally, the structural transformation of kaolinite during calcination included dehydroxylation, sintering, and the formation of mullite. Crystalline kaolinite completely decomposed into semicrystalline metakaolinite at 600–800 °C, accounting for the increase in chemical reactivity. The interlayer sintering of metakaolinite and the recrystallization of amorphous components led to the decrease in chemical reactivity after 800 °C. Furthermore, the thermal behaviors of carbon in KAS are greatly affected by the calcination atmosphere. The presence of carbon reduced the chemical reactivity of calcined KAS. [ABSTRACT FROM AUTHOR]

To improve the fire extinguishing efficiency and reduce the re-combustion risk, a novel approach to fire extinguishing using sodium pyrotechnic aerosol (SPA) was adopted for controlling underground mine fires. Physical simulation experiments of 1 m3 in size show that the extinguishing effect of aerosol consisting of NaNO3 and dicyandiamide is better than that of 0.2 MPa nitrogen, in which the cooling rate peaks at 32.6 °C min−1. Experiments result prove that the N2 and CO2 yield of aerosol reach about 10 mol s−1 m−3 and 5 mol s−1 m−3, respectively. As an additive, phenol–formaldehyde resin embodies advantages compared with agents such as K2C2O4, CH4Mg2O6, and potassium hydrogen phthalate. According to TG/DTG tests, characteristic temperature points of coal with SPA can be increased significantly, and the apparent activation energy of coal also increases to 18.8–80.5%. Theoretically, Na-salt generated by aerosol reaction consumes the O-contained groups in coal and creates an alkaline environment. Abundant N2 and CO2 also carry ultra-fine Na-salt residue continuously suppressing fire. As a new fire extinguishing technique for use in underground coal mines, SPA shows potential for underground fire prevention. [ABSTRACT FROM AUTHOR]

As a significant space–time infrastructure, the Global Navigation Satellite System (GNSS) provides high-precision positioning, navigation, and timing (PNT) information to users all over the world. However, GNSS real-time kinematic (RTK) mobile receiver signal attenuation is obvious in complex environments such as under trees, urban canyons, and indoors, among others, and it is incapable of meeting the demand of multi-level mass users for indoor and outdoor seamless positioning applications. The goal of this study was to address the limitations and vulnerabilities of the GNSS RTK positioning above-mentioned. First, we propose a GNSS RTK/UWB/DBA fusion positioning model and provide detailed algorithm steps for various types of observations. The performance of the GNSS RTK/UWB/DBA fusion positioning under various occlusion environments is then thoroughly evaluated using static and dynamic cart experiments. The experiment results show that as the elevation mask angle increases, the number of available GNSS satellites decreases and the ambiguity resolution success rate decreases; in comparison to GNSS RTK, the proposed GNSS RTK/UWB/DBA fusion positioning model can significantly improve the spatial geometry distribution of observations, reduce the position dilution of precision (PDOP) value, and improve the ambiguity resolution success rate. At an elevation mask angle of 50 degrees, GNSS RTK/UWB/DBA combination positioning can improve the ambiguity resolution success rate by 20% to 60%, and a positioning error less than 5 cm by 20% to 50%. It also indicates that the GNSS RTK/UWB/DBA fusion positioning model has higher positioning accuracy and can effectively improve the availability and reliability of GNSS RTK in a local harsh environment. [ABSTRACT FROM AUTHOR]

In this study, high-ash coal slime-based mineral soil amendment (MSA) was prepared via the hydrothermal method using high-ash coal slime as raw material, supplemented with activator calcium oxide and additive KOH solution. After hydrothermal treatment at 230 °C for 5 h, the original crystalline phase (quartz and kaolinite) of the high-ash slime was completely transformed into hydrotalcite zeolite, tobermorite, and silicate of potassium aluminosilicate, which has the largest specific surface area. The adsorption of Pb2+ and Cd2+ was adherent to the kinetic equation of secondary adsorption and Freundlich models, and the removal of Pb2+ and Cd2+ reached up to 362.58 mg g−1 and 64.67 mg g−1. The successive releases of SiO 2 and CaO from MSA conformed to the Elovich equation, whereas the releases of SiO 2 in Cd-containing environments and CaO in Pb- and Cd-containing environments more closely conformed to the power function; the releases of K 2 O all conformed to the first-order kinetic equation. The presence of Pb2+ and Cd2+ in the environment promotes the release of potassium and calcium elements with MSA's ion-exchange ability, and attenuates the release of silicon elements. Combining Pb2+ and Cd2+ with silicon resulted in the intolerant precipitation of 3PbO·2SiO 2 and Cd 2 SiO 4. The mineral precipitation mechanism is the most important mechanism of MSA in immobilizing heavy metals, accounting for 72.7%–80.5% of the total adsorption. Further contaminated soil immobilization experiments also showed that the application of MSA significantly reduced the bioavailability of soil heavy metals. When the MSA addition amount was 1.6%, the residual state increased by 63.58%. In conclusion, preparing MSA may effectively utilize coal-based solid waste with high added value. [Display omitted] • Mineral soil amendments (MSA) can adsorb heavy metals, such as Pb2+ and Cd2+. • MSA releases multi-nutrients into the soil, and four models were applied to estimate their release in solution over time. • Heavy metals combine with available Si to form residual state and reduce their bioefficacy. • MSA provides soil nutrients and reduces the biological activity of heavy metals, enabling sustainable agriculture. [ABSTRACT FROM AUTHOR]

In low-rank coal (LRC) mixed collectors, little attention has been paid to the structure-activity relationship of different carboxylic acids. In this study, the application effect and adsorption mechanism of the mixed collector composed of dodecane (D) and carboxylic acid with different carbon chain lengths (n-valeric acid (VA), n-decanoic acid (DA), myristic acid (MA)) for LRC were explored by using sum-frequency vibration spectroscopy (SFG) and molecular dynamics simulation (MD). SFG measured the groups orientation angle on the LRC surface treated with the mixed collector, revealing that during the interfacial assembly process of mixed collector molecules, D molecules and the main molecular axes of DA molecules with similar carbon chain length tend to be adsorbed parallel to the LRC surface. The MD results showed that adding D-DA could weaken the hydrogen bonding between the LRC surface and interfacial water to the greatest extent, thereby improving every component's diffusion ability. [Display omitted] • First time to use SFG and MD to study the adsorption and assembly of mixed collectors. • SFG strength calculation illustrated the overall interface adsorption conformation. • MD revealed the dynamic properties and the damage degree of the hydrogen bond network. • Note: SFG (Sum-frequency vibration spectroscopy); MD (Molecular dynamics simulation). [ABSTRACT FROM AUTHOR]

[Display omitted] • Sodium alginate (SA), sodium carboxymethyl cellulose (CMC), chitosan (CMC) and guar gum (GG) can enhance CG pyrolysis. • The Comprehensive Pyrolysis Index (CPI) of the four biomass materials are all higher than that of CG pyrolysis. • The best blending ratio for CG/CMC as 3:1. • Among the four biomass materials, GG has the most positive interactions with CG pyrolysis, followed by CS and SA, while CMC is the least effective. • SA, CMC, CS and GG are beneficial to CG pyrolysis and reduce the harmful gas emissions. Biomass materials are potential to promote coal gangue pyrolysis process. This study investigates the effects of four biomass materials derived from different sources, namely sodium alginate (SA), sodium carboxymethyl cellulose (CMC), chitosan (CS), and guar gum (GG), on the pyrolysis of coal gangue (CG) in a nitrogen atmosphere. Thermal gravimetric analysis coupled with mass spectrometry (TG-MS) was used to analyze the thermal behaviors and emission characteristics of CO 2 , NO x , and SO 2 during the co-pyrolysis process of CG and the four different biomaterial blends, which were mixed in varying ratios. The study investigated that the interactions between the various biomaterials and CG by calculating and comparing pyrolysis parameters, such as the comprehensive pyrolysis index (CPI) of CG and the blends. Additionally, a kinetic analysis using the Kissinger-Akahira-Sunose (KAS) method was conducted to reveal the co-pyrolysis mechanism. The thermal gravity analysis results illustrated that SA, CMC, CS and GG were all conducive to enhancing CG pyrolysis. As the biomass content in the blends increases, the sample experiences greater mass loss, while the initial pyrolysis temperature and residual mass ratio decrease. This suggests the presence of biomass enables more complete pyrolysis reactions of CG. Among the four biomass materials, GG had the most positive effect on promoting CG pyrolysis, followed by CS and SA, with CMC having the least effect. The kinetic analysis showed that the primary step of each blend sample generally conformed to the first-order kinetic model. The calculated activation energies of blends groups were lower than that of CG pyrolysis, verifying the positive effects of the four biomaterials on CG pyrolysis. However, the interaction mechanism varied in different pyrolysis stages for each type of biomass material. Gas emission analysis indicated that the emission of CO 2 , NO x and SO 2 in blends groups were significantly lower than that of CG pyrolysis. This implies that the addition of the four biomaterials could effectively control the emission of carbon dioxide and pollutants during CG pyrolysis. [ABSTRACT FROM AUTHOR]

Cake permeability is a crucial macroscopic physical property in characterizing filtration behavior for coal slurry. However, there is still no appropriate model derived to establish the essential relationship between the cake permeability and complex particle property. In this study, the three-dimensional microstructures with different particle gradation and porosity were generated using particle discrete element software. The permeability of each constructed model was calculated utilizing Lattice Boltzmann Method (LBM). Simulation result shows that the Kozeny–Carman (KC) model is proper to predict the permeability of porous media with different gradations. When the gradation parameters are not considered, it shows that d 30 can best represent the particle size characteristics of the particle systems. When the porosity and average particle size remain unchanged, the permeability increases with the increasing of the non-uniformity coefficient (C u) and the curvature coefficient (C c). Moreover, we proposed an analytical expression for the permeability estimation with different gradation characteristics, which contains the parameters that can be easily measured in engineering. Then a set of coal slurry samples with different particle size distributions were selected to conduct the filtration test, the permeability of each sample was measured to compare with the predicted results of the gradation permeability model. It is clear that the KC equation in this case can not calculate the cake permeability effectively. Although the gradation model is relatively appropriate to estimate the cake permeability, its accuracy still needs to be improved by considering the pore structure property to eliminate the effect of constant terms. [Display omitted] • The effect of particle property on permeability for porous structure was studied. • The permeability value increases with the increasing of particle size and porosity. • Adding coarseparticles to fine-grained porous mediacan increase its permeability. • Fine particle proportion affects permeability of loose and dense graded structures. • LBM is capable of describing the details of flow in granular porous materials. [ABSTRACT FROM AUTHOR]

The preparation of an environmentally friendly and efficient flocculant for solid-liquid separation in industrial wastewater is highly important. In this study, a novel cationic flocculant (AL-g-PAMA) was synthesized by a thermal initiation method using alkali lignin (AL) as the main chain and acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as the grafted side chains. The structure, thermal stability, and surface morphology of the copolymers were investigated by various characterization methods. The results indicated the successful synthesis of AL-g-PAMA. AL-g-PAMA was applied to improve solid-liquid separation in kaolin suspensions. The results showed that AL-g-PAMA had excellent flocculation-sedimentation and dewatering efficiency. When the dosage of AL-g-PAMA #5 was 600.0 g/t(s), the thickness of the compressed layer was 2.2 cm, the floc settling velocity was 24.1 cm/min, and the transmittance of the supernatant was 84.0%. The moisture content of the filter cake decreased from 55.0% to 43.4% after treatment with AL-g-PAMA #5. The results of zeta potential and focused beam reflectance measurement (FBRM) analysis indicated that bridging and electroneutralization were the main flocculation mechanisms. Therefore, this study extends the potential for using lignin as a bioflocculant and provides a feasible approach to efficiently purify high-turbidity wastewater. [ABSTRACT FROM AUTHOR]

This study aimed to increase the ammonium nitrogen adsorption capacity of lignite using ultrafine grinding, aiming to reduce eutrophication in water bodies. Ammonium sulfate (NH4)2SO4 was employed as a stand-in for ammonium nitrogen in water solutions. The lignite sample for adsorption was processed with varying milling times. Adsorption efficacy was assessed primarily through isothermal adsorption tests and other techniques. Additionally, the study delved into the adsorption mechanisms. The results demonstrate that lignite ground for 50 min follows monolayer adsorption, characterized by minimal pore size and reduced diffusion rates, thereby extending the time to reach equilibrium and maximizing adsorption. BET and SEM analyses show that coal powder is effectively ground by zirconia balls in a vertical stirring mill, diminishing its particle size and forming new micropores. Concurrently, larger native pores are transformed into mesopores and micropores, providing numerous sites for NH4+ adsorption. XPS and FTIR analyses indicate an increase in exposed carbonaceous surfaces and oxygen-containing functional groups in ultrafine lignite. Ammonium ions replace hydrogen in carboxyl groups to form COONH4, and hydrogen bonds may form between NH4+ and C-O groups. Additionally, the electrostatic attraction between NH4+ and the coal surface further enhances adsorption. It can be concluded that the physical grinding process increases the specific surface area and creates more active adsorption sites, which in turn, boosts NH4+ adsorption capacity. The maximum equilibrium adsorption capacity is as high as 550 mg/g. This study suggests that ultrafine lignite is a promising material for treating ammonia-nitrogen wastewater. [ABSTRACT FROM AUTHOR]

The recovery of difficult-to-float coal using traditional nonpolar hydrocarbon oil collectors can be challenging, particularly for low-rank or oxidized coal. Thus, there is a need for more efficient flotation agents. Nanoparticle flotation collector technology has become increasingly popular in the field of mineral processing, and the presence of various ions in the slurry can significantly affect the interaction between collectors and mineral surfaces. In this study, cationic polystyrene (PS) nanoparticles were prepared using an emulsion polymerization method, and the effects of Na+ ion concentration on the in situ adsorption and desorption processes, adsorption layer configuration, and adsorption kinetics of PS particles on amorphous carbon (coal model) and SiO2 sensors (quartz mineral model) were analyzed using the quartz crystal microbalance with dissipation (QCM-D) technique. Our results showed that the hydrophobic PS nanoparticles irreversibly adsorbed onto both amorphous carbon and SiO2 sensors under different environmental conditions, and their adsorption capacity decreased gradually with increasing Na+ ion concentration. Increasing Na+ ion concentration from 0 M to 1.0 M resulted in a 24.4% and 30.9% decrease in equilibrium adsorption capacities of PS nanoparticles onto amorphous carbon and SiO2 surfaces, respectively. The adsorption rate of PS nanoparticles onto the SiO2 surface was much greater than that on the amorphous carbon surface. The adsorption rate constant of PS nanoparticles onto SiO2 surfaces was 0.782 at 0.1 M Na+ ion concentration, while its adsorption rate constant onto amorphous carbon surfaces was only 0.060. Moreover, the adsorption process was found to be more in line with the quasi-primary kinetic model. These findings suggest that PS nanoparticles may serve as promising flotation collectors for the recovery of difficult-to-float coal, and highlight the importance of considering the effect of dissolved ions on the adsorption properties of flotation collectors. [ABSTRACT FROM AUTHOR]

An experimental study of the filtration dewatering of fine coal focusing on particle characteristics was carried out. The dewatering behavior was determined by filtration velocity, moisture content and resistance of cake using a vacuum filtration cell. The suitable filtration conditions were explored, the particle grain sizes were tested and filter cake structures were modulated, and the optimum structure of cake modified with kerosene and flocculant agents was determined. Overall, it is found that the amount of the feed particles under 0.045 mm and the uniformity of the feed particles have a direct bearing on the dewatering efficiency. The best filtration enhancement was achieved by the addition of kerosene, which yielded cake moisture ranging from 27.53% to 23.12% compared without any agents. [ABSTRACT FROM AUTHOR]

In recent years, low-cost single-frequency GNSS receivers have been widely used in many fields such as mass navigation and deformation monitoring; however, due to the poor signal quality of low-cost patch antennae, it is difficult for carrier phase real-time kinematic (RTK) technology to fix the integer ambiguity. Differential GNSS (DGNSS) positioning with pseudorange can effectively meet the high robustness and reliability requirements for the submeter to the meter level positioning accuracy of UVA/vehicle/aerospace users. To improve the DGNSS positioning accuracy and reliability of low-cost single-frequency GNSS receivers in complex environments, we propose a differential barometric altimetry (DBA)-assisted DGNSS positioning algorithm, which solves the DGNSS observation equations jointly and rigorously with the Earth ellipsoidal constraint equations constructed by the DBA altitude. The DBA altitude accuracy at different baseline lengths was evaluated in detail, and the DGNSS positioning performance of the single-frequency low-cost u-blox receiver NEO-M8T with a patch antenna and DGNSS/DBA combined positioning performance with the BMP280 barometer was analyzed by several sets of static and dynamic experiments under different environments. The results show that the single-frequency NEO-M8T receiver with patch antenna DGNSS positioning accuracy is submeter level in the static environment and drops to meter level in the dynamic environment. GPS+BDS dual system has higher positioning accuracy than single GPS or single BDS. DGNSS/DBA combination has higher positioning accuracy than DGNSS, especially the root mean square error (RMSE) can be improved by 30% to 80% in the U direction and slightly improved in the N and E directions. This study can provide an effective solution reference for various applications of low-cost sensor fusion positioning in the mass consumer market. [ABSTRACT FROM AUTHOR]

Large-scale application of filled coal mining technology has long been limited by conditions such as the cost of filling. Compared to traditional filling materials, coal flotation tailing filling materials (CFTFM) offers advantages such as low cost and excellent performance. The Box–Behnken response surface method was used to investigate the influence of flotation tailing properties on the mechanical properties and hydration mechanisms of the filling material. Ash content, blending, and calcination temperature of the flotation tailings were used as the investigating factors, and uniaxial compressive strength (7d and 28d), slump, and the slurry water secretion rate of the filling material as the evaluation indicators. The results showed that the influence of the flotation tailings on the uniaxial compressive strength (28d) of CFTFM followed the order ash > calcination temperature > doping, with the interaction of ash and calcination temperature having a greater influence on the uniaxial compressive strength. The optimized pre-treatment conditions for the flotation tailings were 59% ash, 30% doping, a calcination temperature of 765 °C, and optimum uniaxial compressive strength of 7.02 MPa. The effect of flotation tailings on the exotherm of CFTFM hydration was determined using a TAM Air isothermal microcalorimeter, mainly in the induction and acceleration phases. Combined with SEM electron microscopy and IR FT-IR analysis of the hydration products, a descriptive model of the CFTFM hydration mechanism was established. CFTFM hydration can be described in three phases: diffusion, hydration, and hardening. The CFTFM prepared in this study is applicable to the integrated mining and charging synergistic mining technology, which can effectively reduce gangue lifting energy consumption and washing process waste, reduce the cost of filling, and can effectively achieve harmless, resourceful, and large-scale disposal of coal-based solid waste. [ABSTRACT FROM AUTHOR]

In this paper, the flocculation properties of polyethylene oxide (PEO) on kaolinite and the mechanism of adsorption on kaolinite anisotropic substrates were explored. As revealed by the experimental results, the settling rate and removal rate of kaolinite increased with increasing PEO concentration, but too high PEO concentration would cause the small particles to stabilize and become difficult to settle. Furthermore, to probe deep into the interactions between PEO and kaolinite anisotropic substrates, the morphology of adsorbed PEO, interfacial adsorption structure, and dynamic behavior of water molecules were determined by quartz crystal microbalance with dissipation (QCM-D) and molecular dynamics (MD) simulations. The adsorption amount of PEO on different mineral surfaces is in the order of kaolinite > alumina > silica, and the thickness of the adsorption structure formed by alumina is greater than that of silica. As illustrated by the MD simulation results, the adsorption of PEO reduces the concentration of water molecules attached to the kaolinite surface. The PEO forms a double-layer adsorption structure on the 001 surface, while forming a tight monolayer adsorption structure on the 00 1 ¯ surface, weakening the interaction between the surface and the water molecules. The above results demonstrate that the adsorption of PEO effectively weakened the hydration dispersion of kaolinite and promoted the agglomeration of kaolinite particles. [ABSTRACT FROM AUTHOR]

It is important to identify an environmentally friendly and efficient flocculant that can replace polyacrylamide for the solid–liquid separation of coal wastewater. In this study, to explore whether chitosan can be used as an environmentally friendly and efficient flocculant for the solid–liquid separation of coal wastewater, AlCl3–chitosan was used to conduct flocculation–sedimentation and dewatering tests under different chitosan dosages and shear-strength conditions for the prepared coal wastewater. Focused beam reflectance was measured to dynamically monitor the number of refractory fine particles, and the settled flocs were photographed and analyzed with microscopy to explore the effect of AlCl3–chitosan on the flocculation settlement effect and floc characteristics. The synergistic mechanisms of AlCl3 and chitosan were investigated using quartz crystal dissipative microbalance and zeta potential measurement. The results showed that the addition of chitosan can significantly improve the flocculation–sedimentation and dewatering effects of coal wastewater. A reasonable dosage under a certain shear strength is conducive to the reduction of fine slime particles, which results in a compact floc structure, increases the floc size, and improves the settling effect. The synergistic effect of AlCl3–chitosan improved the electric neutralization and adsorption bridging abilities of the chitosan, and the mixed solution of AlCl3 and chitosan had stronger adsorption on the carbon surface. This study provides a new approach to the selection of flocculants for coal wastewater treatment. [ABSTRACT FROM AUTHOR]

The impact of coagulant type and dosage on the clarity, zeta potential, floc size, and floc structure of a coal slurry suspension was investigated. The results showed that the critical coagulation concentrations of trivalent ions are 0.81 mM and 0.018 mM for coal–coal and coal–kaolinite, respectively, which are lower than those of divalent ions. The initial settling was more affected by AlCl3 and FeCl3 than MgCl2 and CaCl2, while the supernatant turbidity was significantly decreased at a lower dosage (0.06 mM) for trivalent ions, consistent with the classical Derjaguin–Landau–Verwey–Overbeek theory, zeta potential results, and adsorption behaviors of quartz crystal microbalance with dissipation. The floc size and settling rate induced by AlCl3 and FeCl3 were greater than those of divalent ions at lower concentrations and tended to have an irregular and porous structure, enhancing the coagulation effect. The findings highlight the differences in the physical characteristics of floc size and structure in optimizing the coagulation process produced by electrical neutralization and sweep-floc coagulation of amorphous metal hydroxide precipitates. [ABSTRACT FROM AUTHOR]

Coal solid waste (CSW) was explored as precursor to prepare porous adsorption material (ACSW) by carbon dioxide activation. The effects of activation method (direct activation and pre-carbonization followed by activation), activation temperature, and activation time were systematically investigated. The burn-off characteristics of the CSW were measured, the ACSW were characterized by field emission scanning electron microscope, gas adsorption instrument and Raman spectrometer, and, in parallel, the adsorption ability was studied using methylene blue (MB) as a typical pollutant. The results showed that compared with direct activation, pre-carbonization reduced the carbon loss, increased the pore volume with pore size less than 1 nm, improved the carbon structural order and increased the MB adsorption performance. In addition, the evolution of the structure of the ACSW strongly depended on the activation temperature and time. With the increase of the activation time, the pore structure evolution underwent three stages: pore forming, expanding, and collapsing. Pore forming mainly involved clearing scattered graphite structures and amorphous carbon. Pore expanding mainly relies on consumption of regular graphite carbon crystal structure. At low temperature of 800 °C, micropores fully developed. As the activation temperature increased to 850–900 °C, pore expansion became apparent, mainly forming pores of 1–5 nm. Moreover, the MB adsorption capacity was positively correlated with the pore volume with pore size less than 5 nm. The burn-off can serve as an indicator for evaluating pore structure and the adsorption performance and when it was ∼25.5 %, the ACSW had the largest pore volume with pore size less than 5 nm and the highest MB adsorption capacity. [Display omitted] • Pre-carbonization reduced carbon loss for ACSW production. • Pre-carbonization increased micropore with pore size less than 1 nm. • Micropores fully developed at low temperature of 800 °C. • Pores of 1–5 nm mainly formed at 850–900 °C. • burn-off can serve as an indicator evaluating pore structure and adsorption capacity. [ABSTRACT FROM AUTHOR]

In this study, in order to improve the flocculation efficiency of natural organic flocculant in coal mine wastewater, guar gum (GG) and [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride (DMC)were used to synthesize a type of graft copolymer of GG with DMC (GG-g-DMC) with flocculating function by free radical polymerization under ultraviolet (UV) light initiation conditions. Performance testing and structural characterization of the composites including FTIR, NMR, XRD, SEM, TG, and XPS were conducted to verify the synthesis of the graft polymer. The GG-g-DMC was applied to treat coal mine wastewater, according to the sedimentation index and the optimal flocculation solution was determined, and the flocculation settling mechanism was studied using focused beam reflectance measurement (FBRM), Zeta potentiometer and adhesion force meter. The results indicated that GG-g-DMC synthesis by UV-initiated polymerization was feasible and the settling effect increased significantly; 0.5 mg/g (s) GG-g-DMC 4 was excellent in all aspects, its sedimentation speed reached 20.64 cm/min, the light transmittance was 95.00%, and the compression layer thickness was 1.89 cm; the mechanism is mainly the synergy of charge neutralization, bridging, and improve hydrophobicity. [Display omitted] • Synthesis and characterization of a new guar gum-based flocculant via UV initiation. • Graft polymer of guar gum shows excellent settling effect in coal mine wastewater. • The mechanisms are charge neutralization, bridging, and improve hydrophobicity. [ABSTRACT FROM AUTHOR]

The accurate estimation and measurement of coal ash are crucial for fuel selection, combustion efficiency assessment and quality control. However, the most widely used ash measurement method is combustion; this method is highly accurate but has a certain lag; additionally, an older radiation measurement method has a certain error. In this regard, in this study, a detection model and measurement method are proposed based on the combination of dual-energy X-ray measurement results and artificial intelligence algorithms, i.e. a coal ash detection model based on a multilayer perceptron (MLP) neural network. A model training database was created, and 6468 raw data points were measured with an experimental apparatus and organized. The results showed that the root-mean-square error between the predicted value and the true value of the trained model was 0.0857. By comparing several indices with the traditional backpropagation (BP) neural network, the root-mean-square error was reduced by 1.27%, and the model’s errors in different predicted output values were uniformly distributed without evident systematic deviation; these results demonstrated and confirmed that our proposed ash prediction model achieved high estimation accuracy and had strong robustness. [ABSTRACT FROM AUTHOR]

During the thickening process, the dosage of flocculant has a great influence on the overflow concentration and filter cake moisture. The dosage of flocculant cannot be automatically updated according to the feeding situation, especially when the properties of the concentrated feeding material change, and the overflow concentration detection feedback cannot be adjusted in time. To address these problems, a dynamic concentration detection device was designed. In addition, a dosage of flocculant correction model based on dynamic concentration detection was constructed, and a feed-forwards flocculant additioncontrol model based on the ISSA-LSTM neural network was proposed. The results showed that the relationship between the linear slope of the dynamic concentration and the dosage of flocculant was in line with that obtained using the ExpAssoc model. Then, a double-layer LSTMslime water feedforward flocculant addition control model was proposed based on the multistrategy jointly improved Sparrow SearchAlgorithm (SSA). This model can determine the optimal dosage according to the condition of the infeeding during the thickening process. This new method can improve the intelligence of coal preparation plants and reduce the cost of washing. The scientific application of these research results will help to realize intelligent solid – liquid separation. [ABSTRACT FROM AUTHOR]

• STAC enhanced the coal slurry dewatering efficiency. • The hydrophobicity of coal tailings was improved by STAC. • The adsorption of STAC on the kaolinite 001 surface was more uniform than 00 1 - face. • STAC inhibited the adsorption of water molecules on the surface of coal tailings. The presence of clay minerals in coal tailings leads to a significant deterioration during the dewatering process. In this study, a cationic surfactant, stearyl trimethyl ammonium chloride (STAC), was considered to enhance the dewatering efficiency of coal tailings. The effect of STAC on coal tailing dewatering was evaluated by the filtration test. Results indicate that STAC can reduce filter cake moisture by increasing the hydrophobicity of particles, decreasing the surface tension of the filtrate, as well as neutralizing the associated charge. Furthermore, to investigate the interactions between STAC and coal tailings, the morphology of adsorbed STAC, interfacial adsorption structure, and dynamic behavior of water molecules were determined by atomic force microscopy (AFM) and molecular dynamics (MD) simulations on an atomic scale. AFM results revealed that the morphologies of STAC adsorbed on coal and kaolinite surfaces differed, owing to distinct interaction mechanisms. The adsorption of STAC on the kaolinite 001 surface is more uniform than on the 00 1 - face and is predominantly based on monolayer adsorption through electrostatic interactions and hydrogen bonding. The MD simulation results suggest that the adsorption of STAC significantly inhibits the attachment of water molecules on coal and kaolinite surfaces. The nitrogen atoms of STAC were adsorbed to the particle surface, such that its alkyl chains were oriented towards water, thereby weakening the interaction between the particles and water. The above findings indicate that the addition of STAC can improve the hydrophobicity of coal and kaolinite effectively and thus, enhance the dewatering performance of coal tailings. [ABSTRACT FROM AUTHOR]

• The microstructure property of filter cake has been developed using X-ray CT. • Pore shape and size, connectivity, tortuosity were characterized quantitatively. • Overall porosity can't be able to explain the filtration results clearly. • The cake structure formed by spherical particle is more favourable for filtration. Solid-liquid separation is an indispensable, challenging and energy-intensive process in the mineral processing industry. An accurate assessment of the filter cake structure is critically important for predicting and controlling the dewaterability of mineral slurries. However, due to the random particle arrangement and complex pore network of filter cake, such microscopic information is difficult to obtain by the current experimental techniques. In this paper, a methodology for identifying and quantifying the microstructure property of filter cake has been developed using X-ray microtomography and tested using the spherical and irregular particles. Several key pore structure parameters, including porosity, pore shape, pore surface area, connectivity, tortuosity, and pore networks, were characterized quantitatively. Combining the filtration experiments, we observe that a single parameter of overall porosity cannot predict the filtration behavior. Spherical particle is more favourable to filtration since its filter cake host better connectivity and lower tortuosity, which appears to affect the filtration velocity and specific resistance. The cake formed by irregular particles has a higher moisture content, which may be caused by its large pore surface area and narrow throat size. These findings demonstrate that X-ray microtomography is more suitable for nondestructive and comprehensive detection of cake structure, compared to conventional methods. This research is expected to provide a comprehensive understanding of the cake structure and a theoretical basis for achieving a high-efficiency solid-liquid separation. [ABSTRACT FROM AUTHOR]

In this work, ultraviolet irradiation was employed to assist in the preparation of a novel photocatalyst composite in the form of carbon dots/zeolite-4A/TiO 2 , using coal tailings as the source of silicon-aluminum and carbon. The composite was designed for the degradation of methylene blue under 500 W of UV light irradiation. Zeolite-4A was used as a support for the well-dispersed carbon dots and TiO 2 nanoparticles. The as-prepared composites were subjected to thorough characterization, confirming the successful formation of zeolite-4A with a cube structure, along with the loading of TiO 2 and coal-based CDs in the composites. The experimental results demonstrated that the UV-CZTs nanocomposites exhibited a remarkable removal efficiency of 90.63% within 90 min for MB. The corresponding rate constant was exceptionally high at 0.0331 min−1, surpassing that of the Dark-CZTs and pure TiO 2. This significant enhancement was possibly due to the synergistic effect of adsorption photocatalysis of the UV-CZTs, combined with the excellent electron-accepting capabilities of the coal-based CDs, which led to highly improved charge separation. An investigation of the spent photocatalyst's recyclability revealed that it retained a remarkable 82.94% MB removal efficiency after five consecutive cycles, signifying the stability of the composite. Trapping experiments also elucidated the primary reactive species responsible for MB degradation, which were identified as photo-generated holes and ⸱O 2 − species. By this process, the hydroxyl radicals generated in the system successfully promoted the transformation of coal tailings to coal-based zeolite and coal-based CDs. Coal-based zeolite served as an excellent carrier of titanium dioxide, which improved its dispersibility. The inhibition of e−-h+ recombination of titanium dioxide by introducing coal-based CDs improved the photocatalytic ability of titanium dioxide. Through this study, coal tailings, as a coal processing waste, were transformed into high-value materials, and relevant photocatalytic composite materials could be prepared with broad application prospects. • A novel preparation method of the composite photocatalysts assisted with ultraviolet-irradiation were proposed. • UV-CDs/Zeolite-4A/TiO 2 composite photocatalysts were prepared using coal tailings as silicon-aluminum source and carbon source. • UV-CDs/Zeolite-4A/TiO 2 were the most stable and reusable because zeolite-4A confined TiO 2 on its surface. • The ternary structure of CDs-Zeolite-TiO 2 enhanced the photocatalytic performance of UV-CDs/Zeolite-4A/TiO 2. [ABSTRACT FROM AUTHOR]

Microfine low-rank coals are subject to metamorphic changes that hinder their floatability, impeding their clean and efficient utilization. The objective of this study was to refine the jet-slurry technique to enhance the floatability of microfine low-rank coals. Furthermore, advanced methods including Focused beam reflectance measurement (FBRM), high-sensitivity microelectromechanical balancer (DCAT), Fourier transform infrared spectrometer (FTIR), and scanning electron microscope (SEM) were employed to dissect the physicochemical effects of jet slurring on microfine low-rank coal particles. The study found that as the concentration of microfine coal particles increased, surface reagent adsorption initially rose and then fell with greater feed volumes. In contrast, adhesion forces displayed an inverse trend. Optimal results were achieved with a feed volume set at 25 L/min. This phenomenon is attributable to multiple regulatory factors. Within certain limits, intensifying conditioning promotes particle agglomeration, curtails fine gangue mineral coverage, boosts sodium dodecyl sulfate (SDS) adsorption, diminishes microfine coal wettability, and better kerosene-coal particle mixing. However, at excessive jet speeds (30 L/min), substantial physical pressure variances and mechanical dispersion forces arise, undermining SDS or kerosene’s chemical adsorption to coal or modified coal, thus reducing reagent attachment. The aforementioned study demonstrates that within certain parameters, jet slurring significantly betters coal-gangue separation, thereby amplifying the flotation efficacy of microfine low-rank coals. This research offers strategic insights into microfine low-rank coal flotation processes and lays a theoretical groundwork for the selection of suitable techniques and reagents. [ABSTRACT FROM AUTHOR]

The evolution law of fluid and solid motion in the initial stage of spiral separation process is critical for mineral particle separation. The current research intends to investigate the fluid and particle motion behaviors in the initial stage of a spiral separation process using a CFD-DEM approach. The results show that the motion behaviors of fluids and particles in the initial stage of spiral separation process could be separated into three states: the development state, the transition state, and the relatively stable state. In the development state, water flows outward with a rapid change of velocity and film thickness. Meanwhile, fluid forced particles to move outward rapidly with no obvious trajectory difference. In the transition state, a collision between the slurry and the outer trough sidewall happens with changing the moving direction of fluids and particles. Following the collision, the flow field distribution tends to be relatively constant, and the light particles progressively migrate to the spiral trough's outer edge, while heavy particles gradually move to the spiral trough's inner edge. [ABSTRACT FROM AUTHOR]

This study investigates the interaction between montmorillonite and polyacrylamide (PAM) with different ionic types using quartz crystal microbalance with dissipation monitoring (QCM-D) and molecular dynamics (MD) simulations. The goal was to understand the effect of ionicity and ionic type on polymer deposition on montmorillonite surfaces. The results of the QCM-D analysis showed that a decrease in pH led to an increase in the adsorption of montmorillonite on the alumina surface. The ranking of adsorption mass on alumina and pre-adsorbed montmorillonite alumina surfaces was found to be cationic polyacrylamide (CPAM) > polyacrylamide (NPAM) > anionic polyacrylamide (APAM). The study also found that CPAM had the strongest bridging effect on montmorillonite nanoparticles, followed by NPAM, while APAM had a negligible bridging effect. The MD simulations showed that ionicity had a significant influence on the adsorption of polyacrylamides. The cationic functional group N(CH3)3+ had the strongest attraction interaction with the montmorillonite surface, followed by the hydrogen bonding interaction of the amide functional group CONH2, and the anionic functional group COO- had a repulsive interaction. The results suggest that at high ionicity levels, CPAM can be adsorbed on the montmorillonite surface, while at low ionicity levels, APAM may still be adsorbed with a strong coordination trend. [ABSTRACT FROM AUTHOR]

The flocculation that takes place in the central feedwell of the thickener plays a crucial role in the coal-slurry thickening process, which is not only complex but also largely influenced by the flow characteristics. A coupled computational fluid dynamics–population balance model (CFD–PBM) was used to model the complex flocculation-thickening behaviour in an industrial-scale gravity thickener. The initialisation parameters of the inlet flow were obtained through self-designed image-recognition experiments, and then the effects of different types of conical deflectors on the floc distribution were simulated and analysed using them. The results showed that, under the condition that the angle of the conical deflector's sides in the vertical plane was known, a reasonable increase in the height of the bottom surface could reduce the annular spanwise vortices at the underflow of the feedwell, thereby avoiding the erosion of the inlet flow and the annular spanwise vortex on the floc deposition layer. However, excessive height on the part of the conical deflector could affect the flocculation effect of solid particles. For the same central feedwell size of the thickener as in the simulation, the best flocculation effect was achieved at an angle of α = 24° in the vertical plane of the conical deflector. Turbulence regulation of the conical deflector promotes the aggregation of fine particles in the fluid of the feedwell, providing a new method for the intensification of the flocculation-concentration process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanism of action of anionic complex surfactants on coal was investigated by AFM and DFT. • The interaction mechanism between the anionic complex surfactant and the coal surface is electrostatic attraction. • The effect of anionic complex surfactants on the wettability of coal surfaces was investigated. • Anionic complex surfactants exhibit better performance on coal surfaces than any single surfactant. The objective of this study was to elucidate the cooperative modification mechanism of anionic composite pharmaceuticals on coal substrates. Composite pharmaceuticals were synthesized using sodium hexametaphosphate (SHMP) and sodium polycarboxylate to reduce coal hygroscopicity. The mesoscopic alteration process between the coal surfaces and the compound pharmaceuticals was examined via atomic force microscopy (AFM). AFM showed that SHMP was multilayer-adsorbed on coal via electrostatic and hydrogen bonding, while sodium polycarboxylate was single layer-adsorbed at the SHMP layer via electrostatic interactions. Composite pharmaceutical adhesion to coal was lower than that for individual pharmaceuticals, indicating synergistic effects. The mechanism underpinning the microscopic synergistic effect of complex pharmaceuticals on the coal surface was further examined using density functional theory (DFT) at the molecular scale. DFT calculations showed that the adsorption energy of SHMP binding to a sodium polycarboxylate molecule was greater than that of SHMP binding to two identical pharmaceutical molecules. The SHMP portion generally interacted with the aromatic coal nucleus via its ring structure, exposing the sodium polycarboxylate carbon chain to maximize the adsorption energy. Combining DFT and AFM provided insight into the composite pharmaceutical function, and a theoretical framework for coal flotation separation was established. [ABSTRACT FROM AUTHOR]

• Ultra-pure anthracite coal was prepared using a vertical stirring mill for deep dissociation. • Flotation under multiple influences were unveiled: physicochemical properties and liberation degree. • Macroscopic have revealed the mechanism by ultrafine grinding affect flotation. • Mesoscopic elucidated the mechanism of ultrafine grinding on surface regulation of anthracite. Anthracite, a valuable and scarce coal, typically requires systematic liberation for deep deashing, wherein the particle size reduces to the micron level upon ultrafine grinding. Changes in the physicochemical properties of anthracite particles induced by ultrafine grinding significantly impact subsequent flotation. Accordingly, in this study, a scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS) system, an Opton IPCAS maceral analyzer, a high-sensitivity microelectromechanical balancer, and an X-ray photoelectron spectrometer (XPS) were employed to investigate the changes in the physicochemical properties of the anthracite particle surface during ultrafine grinding. The flotation efficiency of ultrafine anthracite coal is determined by various factors such as the extent of sample liberation, surface wettability, and the state of inorganic mineral coatings. During the initial phase of ultrafine grinding, the comminution efficiency of the sample is high, leading to a progressive increase in the hydrophobicity. However, suboptimal flotation performance results from inadequate liberation. When the sample is liberated to an ultrafine scale, a higher degree of liberation is achieved. The particle surfaces become increasingly covered with inorganic minerals, accompanied by intensified oxidation, leading to a gradually reduced particle hydrophobicity that impaired the flotation performance. This study advances our knowledge on the mechanism by which ultrafine grinding alters the physicochemical properties of anthracite coal particles and affects the flotation processes. The theoretical framework of this study provides crucial insights for interface regulation in the preparation of ultra-low ash anthracite coal and ultrafine coal flotation. [ABSTRACT FROM AUTHOR]

[Display omitted] • X-ray microtomography is utilized to obtain the microstructural of filter cake. • Particle shape and size can influence the filtration performance and permeability. • LBM is capable of providing detailed flow and predicting the cake permeability. • The permeability depended strongly on tortuosity, pore-throat ratio and pore size. • The fractal model are not appropriate for determining cake permeability. The separation of particulate solids from liquids by filtration constitutes an important stage in many industrial processes. For the study of flows in filter cake, the microstructure and permeability are of critical importance and can influence the efficiency of the fluid flow and mass transfer. In this study, filtration tests are carried out with quartz particles of different size distribution and shapes. Base on this, we combined the X-ray microtomography (XMT) and Lattice Boltzmann Method (LBM) simulation as a comprehensive approach to further analyzed and discussed the influence of particle property on microstructural detail and fluid transport of filter cake. In addition, the permeability of filter cake was predicted by two mathematical models and compared with the numerical and experimental data. From this analysis, it is found that if the particle properties could be specified for a filtration, the target properties would be for the particles to have as large a size as possible, be as near to spherical as possible. LBM is capable of describing the details of flow transport which occurs in filter cake and calculating its permeability. The fluid flux in filter cake strongly depends on flow main channels which is more related to the width of channels than the numbers of channels. Combined with CT test, we observe that improving pore connectivity and pore size is more effective than increasing porosity and number of pores for improving the cake permeability, and decreasing the pore tortuosity can also increase the flow velocity. Both the Kozeny-Carman model and the fractal model are questionable and not appropriate for determining cake permeability. [ABSTRACT FROM AUTHOR]

To mitigate the decrease in the separation efficiency caused by membrane fouling during the operation of polyvinylidene fluoride (PVDF) ultrafiltration membrane, this experiment employed methylacrylic sulfobetaine (SBMA)-modified graphene oxide (GO) nanoparticles improve the antifouling capability of ultrafiltration membrane. In this study, the hydrophilic material SBMA was grafted onto the surface of GO by free radical polymerization to form PSBMA@GO hydrophilic nanoparticles. PVDF ultrafiltration membranes containing GO nanoparticles or PSBMA@GO nanoparticles were prepared by the phase inversion method for comparative testing. The experimental results showed that after the addition of 0.75 wt% PSBMA@GO nanoparticles, the pure water flux of the PVDF ultrafiltration membrane and the hydrophilicity of the surface were the highest. Based on the scanning electron microscopy (SEM) and atomic force microscopy (AFM) results, the pore structure of the cross section was optimal and the surface roughness was the lowest. Based on the results from the cyclic filtration tests of three typical foulants, the PVDF ultrafiltration membrane with 0.75 wt% PSBMA@GO nanoparticles had the best antifouling capability. Furthermore, the extended Derjaguin Landau Verwey Overbeek (XDLVO) theory was used to explore the interaction energy between foulants and the membrane when in close contact. The results showed that compared to the addition of the GO nanoparticles, the PVDF ultrafiltration membrane with the addition of the PSBMA@GO nanoparticles exhibited a lower attractive interaction energy with foulants. Therefore, the addition of the hydrophilic nanoparticles modified by the hydrophilic material SBMA to ultrafiltration membranes provides a potential new method to improve the antifouling capability of these materials in the future. [Display omitted] • Zwitterionic polymer poly sulfobetaine methacrylate as a modified material can improve the hydrophilicity of graphene oxide. • Bovine serum albumin, humic acid and sodium alginate were selected to represent the antifouling performance of natural sewage on ultrafiltration membranes. • The interaction energy calculated by XDLVO theory can predict the adsorption and reaction behavior of foulant colloid on the membrane surface. [ABSTRACT FROM AUTHOR]

Clay-rich coal slurries suffer from low yield and high ash content during flotation. In this study, the effective recovery of clay-rich coal slurries was facilitated by pretreatment with sodium hexametaphosphate (SHMP) and sodium polycarboxylate complex surfactants. Contact angle and adhesion force tests show that complex surfactants reduce the wettability of the coal. Fourier transform infrared (FTIR) spectroscopy shows that the ring structure of SHMP leads to P-Π stacking with the benzene ring structure on the coal and hydrogen bonding with the oxygen-containing functional groups. Sodium polycarboxylate can combine with the hydroxyl groups on the coal and the oxygen-containing functional groups exposed after multipoint diffusion coverage of SHMP by the multihydroxyl structure on the chain. Atomic force microscopy (AFM) tests show that the complex surfactant is adsorbed on the coal surface by hydrophobic and electrostatic attraction. Adsorption occurs in the form of single- and double-layer adsorption. Zeta potential measurements and scanning electron microscopy (SEM) results show that the addition of a complex surfactant attenuates slime entrainment. Flotation tests show that after pretreatment with the surfactant complex, the cleaning coal yield is increased by 45.14% and the ash content is decreased by 7.92% compared with froth flotation. The flotation effect shows an obvious improvement. The above results help to elucidate the mechanism for composite surfactants to improve the flotation separation effect based on mesoscopic and microscopic aspects and strive to provide theoretical support for efficient flotation. [Display omitted] • The efficient mixture of SHMP and sodium polycarboxylate exhibited superior modification properties. • After the modification, the adhesion and wettability of the coal is significantly reduced. • At the ratio of 5:3 of the complex surfactants, SHMP provided the best adsorption site for sodium polycarboxylate. • The mechanism of the interfacial action of the composite surfactant on the coal slurry was studied. [ABSTRACT FROM AUTHOR]

Solution pH plays a vital role in the interactions between polymer flocculants and solid colloid particles which determines the flocculation performance. The influence of solution pH on the flocculation of Magnafloc5250 on ultrafine coal suspension and the interactions between the polymers and solid surfaces were investigated by using atomic force microscopy (AFM), hydrodynamic radius measurements, particle floc size analyses, and flocculation dewatering tests. Our results revealed that the settling velocity and supernatant transmittance of ultrafine coal suspension without flocculant were low in alkaline conditions due to the strong repulsion, which agreed with the extended DLVO theory and direct force measurements by AFM. In the presence of Magnafloc5250, the highest transmittance was observed at pH 4 due to the compressed electric double layer among the coal particles, while the settling velocity reached a maximum value at pH 10, which was consistent with the largest average size of flocs (41.80 µm) and more extended conformation of flocculant. The adhesion force measured by AFM was divided into two parts: flocculation force and bare force. And the flocculation force reached a maximum value with the broadest range of action at pH 10, which supported the settling tests and floc size measurements well. The strengthened bridging interaction (e.g., via hydrogen bonding) with increasing solution pH is attributed to the increase of effective binding sites between more extended polymer chains and coal particles, thus contributing to an enhanced flocculation behavior. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • CPAM still played its role as a polymer flocculant, the addition of α-HH promoting the formation of flocs. • In the CPAM system, the hydration reaction of α-HH could be accelerated to produce many CaSO 4 ·2H 2 O crystals. The CaSO 4 ·2H 2 O crystals could effectively play the role of skeleton support in the filter cake. • The CPAM and α-HH synergistic regulation effectively improves the dewatering performance of coal slurry. • The whole dewatering process was divided into four stages, and the filtering performance of filter aids was analyzed from the point of view of cake compressibility. • The conditioned coal slime dewatering effect was measured using a newly designed pressurized dewatering device. To improve the filter cake structure and efficiently dewater coal slime, CPAM and α-HH were designed for combined use in filtration experiments. The conditioned coal slime dewatering effect was measured using a newly designed pressurized dewatering device; the auxiliary mechanisms were analyzed from various perspectives, including hydrophobicity, electrostatic repulsion, coal slime composition and filter cake structure. A CCD experiment indicated that the optimal concentrations of the two additives in combination were 205.90 g/t CPAM and 56.25 mg/g α-HH. Under these conditions, the coal slime water CST decreased to 31.6 s, the filtration rate increased to 177.01 mL/(s·m2), the filter cake moisture content decreased to 16.46%. CPAM still acted as a polymer flocculant, causing the coal slime particles to form large flocs, while the addition of α-HH reduced the absolute zeta potential of the filtrate to 1.36 mV, thus decreasing the static repulsive forces between coal slime particles, promoting floc formation and increasing the floc chord length to 83–185 μm. These effects enhanced the CPAM flocculation effect. In the CPAM system, these phenomena accelerated the hydration reaction of α-HH and produced many CaSO 4 ·2H 2 O crystals. These crystals formed an interwoven skeleton in the coal slime flocs, increasing the CDI increased to 1650.04, and increasing the filter cake porosity from 13.26% to 16.45% and effectively improving the filter cake pore connectivity and permeability, which improved the filtration effect. This study could provide a new method and perspective for the efficient pressurized dewatering of coal slime. [ABSTRACT FROM AUTHOR]

Separation performance of mechanical flotation cell and cyclonic microbubble flotation column (FCMC) was compared in terms of the beneficiation of high-ash coal fines that has the characteristics of the content of <0.045 mm accounting for more than 50% of the flotation feed and the ash content of <0.045 mm being more than 50%. The optimal experimental results of the mechanical flotation were determined as the flotation perfection index η of 47.37%, the clean coal yield of 39.19% and the clean coal ash content of 10.78% at the feed pulp concentration of 40 g/L through twice explorative flotation experiments and the orthogonal experiment. It was found that the ash content of the clean coal had a strong dependence on the feed concentration. In contrast, the yield of the concentrate of the column flotation was increased to 43.26% with the lower ash content of 9.47% and the higher η of 54.51% even at higher feed concentration of 60 g/L. The remarkable separation efficient of the FCMC flotation column for the difficult-to-float coal slime that has the characteristics of high content of fine particles with high ash was attributed to the presence of the centrifugal force field, more microbubbles generated by hydrodynamic cavitation, the form of countercurrent mineralization, and thicker froth layer. [ABSTRACT FROM AUTHOR]

• Spreading force increased with decreasing advancing contact angle. • Spreading force for methylated glass was lower than reported for polymers. • Adhesion force increased with decreasing value of the most stable contact angle. • Maximum adhesion forces for methylated glass and smooth polymers are similar value. Measurements of the spreading and capillary forces for liquids deposited on solid surfaces of varying surface chemistry and topography are a prerequisite to better understanding and quantification of the wetting mechanisms. In this study, glass slide surfaces were modified with trimethylchlorosilane to fabricate surfaces of varying hydrophobicity. Then, the forces of spreading and adhesion were measured between water droplets and glass surfaces using a high-sensitivity microelectronic balance. Integrated with a digital camera, the experimental set-up recorded forces and water droplet deformations during water droplet attachment, spreading, compression and retraction processes. It was confirmed that the spreading force increases with decreasing advancing contact angle for methylated glass, following a similar correlation as observed for smooth and rough polymers. However, the spreading force values for methylated glass were a few times lower than reported for polymers in spite of a similar roughness characteristic. It was also confirmed that the maximum adhesion force between water droplet and methylated glass increases with decreasing value of the most stable contact angle, a correlation that is similar to that reported for smooth polymers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation and measurement methods of surface roughness are reviewed. • The effect of roughness on particle-bubble interaction is discussed systematically. • Novel concepts are proposed and emphasized to reveal the role of surface roughness. • The prospects for future research in mineral flotation are put forward. Particle roughness affects flotation recovery in terms of wettability, kinetics, bubble-particle interactions, and even inter-particle aggregation. The influence of the surface roughness of particles on flotation recovery and their underlying mechanisms have been proven to be important. To achieve this goal, researchers have used a variety of industrial minerals or natural hydrophilic/hydrophobic materials to demonstrate the effect of morphological characteristics on particle-bubble adhesion, detachment processes, and flotation rates and recoveries. However, the current conclusions are not uniform and the findings vary with the materials used. Therefore, the preparation, as well as measurement methods used in the current studies on flat surfaces, and the effects of particle surface roughness, are summarized and discussed in this paper, respectively. The effects of roughness on the contact angle, induction time, particle-bubble interaction energy, and flotation effectiveness are reviewed. A systematic review of the relevant literature from recent decades is presented with the expectation of shedding light on the underlying mechanisms behind the inconsistent findings and providing instructive guidance for future studies focusing on the effect of surface roughness on particle-bubble interactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The differences of sodium polycarboxylate on carbon and kaolinite were studied. • Increased clean coal yield and reduced clean coal ash through sodium polycarboxylate flotation pretreatment. • The addition of sodium polycarboxylate significantly enhanced the hydrophobicity of carbon and the hydrophilicity of kaolinite. • The addition of sodium polycarboxylate enhanced the separation of useful and veinstone minerals. Kaolinite-rich coal slurries suffer from a low yield and high ash content owing to the easy mudification of kaolinite in water during flotation. This study investigates the efficient recycling of a kaolinite-rich coal slurry using sodium polycarboxylate flotation pretreatment. The differences in the mechanism of action of sodium polycarboxylate on coal and kaolinite were investigated using high-sensitivity microelectromechanical balancer (DCAT), Fourier infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results show that sodium polycarboxylate reduces the adhesion of the coal slurry and increases the adhesion of kaolinite. Sodium polycarboxylate can cover the hydrophilic groups of –OH by binding to the hydroxyl groups on the coal surface at multiple points via the polyhydroxy structure on the molecular chain. Covering the hydrophobic potential of kaolinite increases the percentages of hydrophilic groups such as Si-O and OH in FTIR. The above findings help to elucidate the separation mechanism of sodium polycarboxylate on carbon ash and improve the flotation separation effect. The optimum dosage of sodium polycarboxylate is 4 kg/t, kerosene, and 2-octanol are 10 kg/t and 12 kg/t, respectively. The yield of clean coal is 70.43 %, ash content of clean coal is 12.62 %, which increases the yield of clean coal by 40.89 % and decreases the ash content of clean coal by 8.56 % compared to the optimum dosage of froth flotation. [ABSTRACT FROM AUTHOR]

The hydration and ion adsorption of kaolinite, which is the most common clay mineral, play crucial roles in engineering geology and environmental applications. To investigate the effects of different valence metal cation solutions on the hydration of kaolinite, we used microcalorimetry, quartz crystal microbalance with dissipation monitoring (QCM-D) and molecular dynamics (MD) simulations to measure the hydration heat and adsorption behaviors between kaolinite and different concentrations of NaCl, MgCl 2 , and AlCl 3 solutions. Based on the results obtained from microcalorimetry, the heat generated by the mixing of kaolinite with different ionic solutions increases with increasing metal cation valence and ion concentration. The QCM-D shows that the increase in the ion concentration leads to an increase in the adsorption volume of metal ions on the kaolinite surface. The adsorption priority of the metal ions on the kaolinite surface can be ranked as Al3+ > Mg2+ > Na+. The results of MD simulations show that the ability of hydrated ions to destroy the hydrated films on the kaolinite surface increases with the increase of the metal cation valence, while a new thicker and more dilute ion hydration structure can be easily formed. The adsorption of ions on the kaolinite surface is controlled by the crystal structure of kaolinite. [Display omitted] • The adsorption of metal ions increases with the ion concentration. • The adsorption can be ranked from high to low as follows: Al3+ > Mg2+ > Na+ • The ion hydration adsorption is affected by the crystal structure of kaolinite. • The metal cation adsorption capacity of kaolinite is higher than that of Cl-. [ABSTRACT FROM AUTHOR]

• Coal macerals were characterized by AFM both in area and aqueous. • Interaction between the montmorillonite 001 surface and silica were measured. • Chaotrope or kosmotrope properties of the 001 surface were proposed. • Liptinite is attractive with the artificial "kosmotropic surface", vice versa. In coal beneficiation, the clean coal would be easily contaminated with the super fine montmorillonite particles coating on it. This interaction between coal (hydrophobic) and montmorillonite (hydrophilic) surfaces is the interactions between the asymmetric systems. Previous studies detected the force between the montmorillonite and graphite or between the montmorillonite mounted tip and coal substrate to represent the interactions between 001 surface and coal. However, there is still lack of experimental direct measurement on the interaction between montmorillonite 001 surface and coal macerals. In this study, proposes methods for determinine the interactions between coal macerals and 001 surface of Na-, K- and Ca- montmorillonite directly by using an atomic force microscope (AFM). The results indicate that the 001 surface of Na- and Ca- montmorillonite served as the chaotropic and kosmotropic surface when it is adjacent to coal surfaces, with an attractive force and repulsive force occurring between them, respectively. The 001 surface of K-montmorillonite served as the chaotropic surface and kosmotropic surface while it is close to liptinite and inertinite, respectively. This chaotropic or kosmotropic property of the surface is determined by the coordination number of the cations and wettability of the hydrophobic surface simultaneously. [ABSTRACT FROM AUTHOR]

Montmorillonite is always a troublemaker for the dewatering in coal processing since its existence can decrease the rates of sedimentation and filtration of coal slurry. To eliminate the adverse effect of montmorillonite, adjusting the slurry pH and adding electrolytes are always the key methods. However, the underlying mechanism still needs to be further studied. The dewatering of Na-montmorillonite (Na-Mt) suspensions has been studied as a function of NaCl concentration (10−3, 10−2, and 10−1 M) at different pH values (6.0, 7.7, 8.1, 9.2). The point of zero charge of edge surface of Na-Mt (pHPZC,edge) appeared at the pH value of 6.8. The sedimentation and rheology experiments described the coagulation and flow behaviors of Na-Mt suspensions, respectively. The Na-Mt suspension coagulated spontaneously at low salt concentration with the pH ~ 6.0. For the pH > pHPZC,edge, the height of the sediment bed reduced and apparent viscosity increased with the increase of the electrolyte concentration. The filtration properties were evaluated on the basis of Darcy's law. The obtained result clearly demonstrated that the filtration rate was accelerated with the increase of pH and electrolyte concentration. The modes of particle association and its effect on filtration performance were discussed. Moreover, a comparison with related results from the literature was performed. At pH ~ 6 and low electrolyte concentration, the positively charged Edge surfaces and negatively charged Face surfaces coagulate rapidly to form a sealed structure by electrostatic attraction. Furthermore, inside this sealed structure, the water molecules cannot be removed in the filtration process easily. However, by increasing the electrolyte concentration at pH > pHPZC,edge, the gradually formed Face/Face structure increases the filtration rate sharply because of the inhibiting effect of the electric double layer (EDL) and the osmotic expansion. Therefore, adjusting solution conditions of the aqueous suspension to tune the particle coagulation behavior is one of the effective methods to solve the problem of montmorillonite dewatering. [ABSTRACT FROM AUTHOR]